1. Field of the Invention
The present invention relates to an air-fuel mixture control device of an engine to be used for vehicles such as motorcycles, and more particularly to an air-fuel mixture control device for controlling a mixture of fuel and air to be supplied to a combustion chamber of an engine.
2. Description of Related Art
Heretofore, there is a case where a fuel injection device is used as, for example, an air-fuel mixture control device to be used in a motorcycle. One of such the devices is provided with a throttle body including an intake passage, a fuel injection valve for injecting fuel into the intake passage, a fuel pump for supplying under pressure the fuel to the fuel injection valve, a pressure regulator for regulating the pressure of fuel to be supplied to the fuel injection valve, a fuel filter for removing foreign materials from the fuel to be supplied, and an electronic control unit for controlling the quantity of fuel to be injected from the fuel injection valve.
In the above device, generally, the throttle body, the fuel injection valve, the fuel pump, the pressure regulator, the fuel filter, the electronic control unit, and other components are mounted separately in respective corresponding positions in a vehicle. In particular, the fuel pump and the pressure regulator are normally incorporated in a fuel tank. On the other hand, the components used for fuel supply (fuel-system component), such as the throttle body, the fuel injection valve, the fuel pump, the pressure regulator, and the fuel filter, individually include somewhat dispersion in fuel flow quantity. Thus, each engine would include the cumulative dispersion in fuel flow quantity due to assembly of the fuel-system components. This causes the generation of dispersion in air-fuel ratio among engines. To reduce the dispersion in air-fuel ratio, each fuel-system component needs machining with high accuracy.
However, the increase of machining accuracy could not fully compensate malfunctions caused by the flow quantity dispersion in the fuel-system components. Hence, there is a conventional case where, for example, during a manufacturing process of an engine, a test run of an engine after completely assembled is made by putting the engine on a lapping table and then applying a predetermined load to the engine. At this time, a fuel injection quantity and output of the engine are measured, and the fuel injection quantity and the engine output are regulated to predetermined set values.
Japanese Patent Unexamined Publication No. 10-159622 discloses an engine output automatic adjusting device related to the above test run. With this automatic adjusting device, an engine in which the fuel injection quantity is controlled by an electronic control unit is test-run under a predetermined condition. The engine output during the test run is detected by a torque sensor. A deviation of a detected value from a target value is then calculated. The calculated deviation is stored in advance in a nonvolatile memory in the electronic control unit. In subsequent operations, a fuel injection quantity is controlled on the basis of the deviation value. To be more specific, during engine operation, a fuel injection quantity is calculated based on values of an engine rotational speed, a throttle opening degree, and others, and then the calculated value is corrected based on the above deviation value. The control of engine fuel injection quantity is executed based on the above correction value of a fuel injection quantity so that the dispersion in the fuel injection quantity is reduced according to the characteristics of each individual engine.
In the conventional device disclosed in the above publication, the fuel injection quantity is corrected based on the engine output torque, which results in total correction of plural factors such as the individual dispersion in flow quantity in the fuel-system components, the dispersion in engine friction, and others. As a result, the conformity of the air-fuel ratio to a request air-fuel ratio would be insufficient, causing a possibility of deterioration in the emission of the engine.
Furthermore, the conventional device conducts the test run for test with respect to an engine assembly, which causes an increase in size of testing equipment.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an air-fuel mixture control device of an engine, capable of reducing the influence of dispersion in fuel flow quantity in each of a fuel injection valve and fuel supplying devices, on an air-fuel mixture, and thereby improving the conformity of an engine air-fuel ratio.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided an air-fuel mixture control device for controlling a mixture of air and fuel to be supplied to a combustion chamber of an engine, the device including: a throttle body including an intake passage communicated to the combustion chamber and a throttle valve provided in the intake passage; a fuel injection valve for injecting the fuel into the intake passage; a fuel supplying device for supplying the fuel under pressure to the fuel injection valve; and an electronic control unit for controlling an injection quantity of the fuel to be injected from the fuel injection valve; wherein the throttle body, the fuel injection valve, the fuel supplying device, and the electronic control unit are united, forming an assembly.
According to the above structure of the invention, the throttle body, fuel injection valve, fuel supplying device, and electronic control unit are united as an assembly, so that the air flow rate characteristics related to the air to be allowed to flow in the intake passage through the throttle valve and the fuel injection quantity characteristics related to the fuel to be injected into the intake passage through the fuel supplying device and the fuel injection valve are determined in each assembly, or air-fuel mixture control device, which differ from assembly to assembly. Accordingly, in each individual assembly, the fuel injection quantity into the intake passage is regulated and the air flow rate in the intake passage is also regulated. This makes it possible to control the characteristics of an air-fuel mixture to be produced in the intake passage in each assembly, separately from an engine body.
The test on the dispersion related to the fuel injection quantity in each assembly is conducted, so that a correction value determined based on the dispersion can be stored in the memory. At the control of the fuel injection quantity, the electronic control unit refers to the correction value stored in the memory. Consequently, the dispersion in the fuel injection quantity in each assembly can be corrected on an individual basis. Thus, the characteristics of an air-fuel mixture can be standardized.
The air-fuel mixture control device may further include a memory for storing a correction value to be used for correcting dispersion in the fuel injection quantity, the memory being provided in the electronic control unit.
Preferably, the fuel supplying device includes a fuel filter and a pressure regulator which are integrally combined by caulking.
Preferably, the fuel supplying device further includes a fuel pump, and the combined fuel filter and pressure regulator are arranged perpendicularly to the fuel pump.
Preferably, an intake condition detector for detecting an intake condition in the intake passage is provided in the united assembly.
Preferably, the electronic control unit controls the fuel injection quantity based on at least the intake condition detected by the detector.
According to another aspect of the present invention, there is provided an air-fuel mixture control system for controlling a mixture of air and fuel to be supplied to a combustion chamber of an engine, the system including: a throttle body including an intake passage communicated to the combustion chamber and a throttle valve provided in the intake passage; a fuel injection valve for injecting the fuel into the intake passage; a fuel supplying device for supplying the fuel under pressure to the fuel injection valve; and an electronic control unit for controlling an injection quantity of the fuel to be injected from the fuel injection valve, the throttle body, the fuel injection valve, the fuel supplying device, and the electronic control unit being united, forming an assembly; a memory for storing a correction value with respect to dispersion related to the fuel injection quantity determined by a preliminary test on an assembly-by-assembly basis, the memory being provided in the electronic control unit; and the electronic control unit being operated to correct the fuel injection quantity based on the correction value stored in the memory for control of the fuel injection quantity.
In the above air-fuel control system, preferably, the preliminary test includes controlling the fuel injection valve to inject the fuel by a predetermined request injection quantity under a predetermined injection signal, then measuring an actual injection quantity of the fuel injected from the fuel injection valve, and determining a deviation of the measured value with respect to the request injection quantity as the dispersion in the injection quantity.